There is a requirement to sense or detect the level of solid or particulate matter such as grain or rice in a holding vessel. With ice banks of a beverage dispense system it is the thickness or weight of ice formed that requires measurement. Previously, ice in an ice bank has been detected by one of three methods. A first method uses a temperature operated switch arranged to detect the water temperature in the ice bank which is indicative of the ice formed. This temperature approach suffers from inherent inaccuracy and a wide differential in performance of switches. Furthermore, location and maintenance of the switch is essential to achieve reasonable results.
A second approach is to employ a mechanical switch which is effectively displaced as the ice grows within the ice bank. Again, the problems of inconsistency are present, and in addition, it is important to ensure the mechanical switch has an actuator that is displaced by the surface of the ice and does not become enveloped within the ice.
A third method involves the use of two electrical probes. An electrical current is passed between the probes and the conductance is drastically altered as ice is formed there between. Obviously, this method has problems of electrolysis of the probes along with disposition of dirt and dissolved salts thereon. Furthermore, this method is affected by the electrolyte content of the supplied water, so each system must be initially set up by experienced personnel.
Accordingly, it would be highly desirable to have an ice bank sensing system that is reliable, accurate, an not generally affected by water electrolyte levels.